Sheriff was a title usually used by law enforcement officers.
Boss Dogg was a cartoon dog and the sheriff of Zanytown. He was created by the fantasies of a young girl who crashed on the Crooked World. (PROSE: The Crooked World)
The Eleventh Doctor referred to himself as a sheriff when defending the town of Christmas on Trenzalore. (TV: The Time of the Doctor)
The Sheriff of Nottingham tried to seduce Clara Oswald into becoming his consort when he took over the Earth. (TV: Robot of Sherwood)
Bat Masterson was the sheriff of Tombstone, Arizona. In October 1881, he and Wyatt Earp rescued Steven Taylor from the Clantons. He later deputised the First Doctor to talk the Clantons out of fighting. (TV: The Gunfighters)
A Zygon had taken the form of C. Norlander, the sheriff of Truth or Consequences. (TV: The Zygon Invasion)
During the 22nd century Dalek occupation of Earth, human sheriffs were converted into Robomen by the Daleks. The Fifth Doctor and Nyssa encountered converted sheriffs in Kansas in 2158. (AUDIO: The Mutant Phase)